Patch antennas, or microstrip antennas are widely used in the wireless, radar, automobile, military, and space industries. Patch antenna technology offers low-profile, low-cost features that are fundamental for the wireless and communication industries. Cell phones, GPS, use dual-polarized antenna elements and also antenna elements configured in arrays to increase gain and to focus directivity.
One important application for a patch antenna is in meteorology. Dual polarization diversity is often used in meteorological radar to improve the accuracy of radar measurements, for example to better characterize hydrometeors. In addition to providing improved hydrometeor classification and precipitation estimation, polarimetric radar may also provide multi parameter measurements that reveal the detailed microphysics of storms. Dual-polarized antennas may be integrated into instruments in satellite, airborne synthetic aperture radar (SAR), two-dimensional electronically-scanned radar, and dual-polarized planar phased array radars.
In phased array radars, the accuracy of measurements obtained are particularly vulnerable to the features of the dual-polarization. For example, differential reflectivity (ZDR) is particularly vulnerable to changes in the polarization basis. The range for ZDR values for hydrometeors varies from approximately 0.1 dB for drizzle and dry snow to 4 dB for heavy rain and large drops. In order to obtain accurate results, the measurement error for ZDR must be on the order of 0.1 dB. To obtain such low ZDR error values, an antenna must feature high polarization isolation (optimally >25 dB for alternate transmit) and high match (optimally <7%) between the main beam antenna power patters.
Polarization isolation below −25 dB is difficult to obtain using prior art dual-polarized planar patch array antennas. While some dual-polarized patch antenna designs may provide low cross-polarization (below −30 dB) in the vertical and horizontal planes, previous designs have failed to provide cross-polarization better than 20 dB in the diagonal plane where the coupling between fields in H and V are significantly higher. In order to overcome this limitation, electronically scan phased array radars have been designed to perform in the principal planes only.
What is needed is radiating element that provides greater isolation in the diagonal plane, with a high match between the co-polar beam antenna patterns for both polarizations (H and V), for both in use as a single element or in a finite planar array.
The present Application overcomes these and other problems and an advance in the art is achieved. The dual-polarized patch antenna element proposed overcomes the problems of isolation in the diagonal plane and mismatch between the horizontal and vertical co-polarizations by combining the features of a parasitic crosspatch antenna and a ground plane with a cross-shaped aperture and capacitive and inductive loading corners.
Independent-fed networks are used to excite the horizontal and vertical polarization components. The dual-polarized patch antenna design also results in low costs and simplified manufacturing.